Internal reflections and nonlinear effects interplay in non-ideal JTWPA

The paper investigates the interplay of nonlinear effects with the non-ideal transmission properties of a Josephson Travelling Wave Parametric Amplifier (JTWPA). Experimental characterization using a microwave and DC cryogenic setup reveals periodic transmission modulation linked to the tuning of the Josephson inductances embedded in the line. The effects of impedance matching and resonant parametric down-conversion (PDC) are observed on a broadband scale, and the impact of design parameters and fabrication issues on device performance is analyzed. These findings contribute to the optimizing techniques for JTWPA devices, advancing quantum-limited amplifiers.